This invention relates generally to conveyor belts and, more particularly, to conveyor belts having a thin film sensor-activating coating.
Conveyor systems have long been utilized in various manufacture and production applications. Conveyor systems, such as incorporating one or more conveyor belts, commonly make use of various mechanisms to activate or trigger certain actions to be performed by equipment associated with the conveyor belt. Such actions include, but are not limited to, sorting, labeling, counting, indexing, and packaging, for example. Common or typical activating or triggering mechanisms employed in such applications can include: a product on the conveyor belt, a tray or other mechanical means attached to the conveyor belt, or a mechanism associated with the pulley system associated with the conveyor belt, for example.
It is known to either sense the presence of a product or item or to sense one or more features or characteristics, such as color, metal content, magnetic content or conductivity, for example, of a product or item being transported or conveyed via a conveyor belt. It is also known to use metal rods and proofing, forming and molding trays attached to a conveyor belt surface or comprising the conveyor belt surface for the purpose of actuating or triggering an action by the equipment associated with the conveyor belt.
For example, U.S. Pat. No. 5,231,919, issued 3 Aug. 1993 and whose disclosure is hereby incorporated by reference, discloses the use of detectable means, such as in the form of metal tabs or strips, attached at predetermined spacings along the surface of a conveyor belt. In accordance with one specifically disclosed embodiment, metal strips of cold rolled steel of 0.005 inches thickness by 0.50 inches wide by 2.50 inches long are attached to a conveyor belt by affixing a polytetrafluoroethylene (PTFE) coated fiberglass belt material patch to the belt surrounding each of the metal strips.
Unfortunately, the attachment of a metal-containing pouch to a PTFE coated fiberglass belt surface presents various problems and complications and is subject to various limitations. First, PTFE coated fiberglass belts typically range in thickness from about 0.008 inches to 0.014 inches (depending on the fabric style). Thus, the addition of a pouch and a metal tab or strip held therein can significantly alter the thickness of the conveyor belt device in the vicinity of the metal strips. For example, devices commercially available from Lawrence Equipment, Inc., the assignee identified on U.S. Pat. No. 5,231,919, and which devices included conveyor belts with such pouches and detectable metal strips, have been analyzed and the dimensions thereof have been measured. In particular, such commercially available devices have been found to contain such metal strips formed of stainless steel and measuring 0.007 inches thick by 0.25 inches wide by 1.75 inches long. Thus, the inclusion of such a pouch and metal strip brings total thickness at the pouch to approximately 0.028 inches and 0.040 inches, respectively, or approximately 4 times the thickness of an original 0.008 inch thick belt surface. As will be appreciated, the inclusion of such metal strips constitutes a significant difference in thickness that can present problems and complications as the belt rides over pulleys, such as resulting in the distortion of the conveyor belt, and in some cases, belt ripping and tracking issues.
Second, due at least in part to the large variation in thickness in the vicinity of the metal strips, such belts must typically be run with the pouches and associated metal strips on the inside of the conveyor belt so it does not distort the products being pressed on the belt surface. Additionally, since such pouches are joined or attached to the belt, the pouches themselves as well as the attachment to the belt are susceptible to grease and oil such as present in products or items conveyed on the belt and such as may be pressed thereagainst. Moreover, if one were to operate the belt with the pouches and associated metal strips on the outside of the conveyor belt, such grease and oil could undesirably act to saturate the pouch such as to result in the pouch delaminating from the surface of the conveyor belt.
Third, such pouch and metal strip-including conveyor belts can be very time consuming to prepare or manufacture. For example, such pouch and metal strip including conveyor belts typically require or involve, in some selected order, appropriately cutting the material pouches and the metal strips, respectively, to desired sizes and shapes; appropriately measuring and marking the belt to indicate the locations for the steel strips and pouches; appropriately attaching the material pouches to the belt surface and appropriately placing the steel strips on the belt. The time required for such belt preparation or manufacture can typically amount to 30 minutes or more per belt.
Finally, this patent specifically mentions the use of cold rolled steel metal strips. Rolled steel is rigid, and when cut, has sharp corners or edges. Conveyor belts such as formed of fiberglass coated with PTFE, as in this patent, are susceptible to tearing under pressure. It will be appreciated that a conveyor operating with a belt having such pouches on the inside of the belt, can be more prone to stresses such as resulting the metal strip containing pouch running over a pulley in the conveyor assembly and such as may result in such metal strip being undesirably pushed through either the surface of the belt or the pouch.
In view of the above, there is a need and a demand for improvements in conveyor belt devices such as to facilitate or otherwise improve the incorporation or use of such conveyor belt devices in conjunction with associated equipment or machinery. In particular, there is a need and a demand for a conveyor belt device and associated combinations which include or incorporate a sensor-activating material in a form that is effective and yet does not unduly hinder the conveyor or the operation of the conveyor and associated equipment.